Issue RedisLabs#204, Disable READ/WRITE events if no requests sent

In cluster mode, where there are few requests with many shards, some
of the shards might not send any requests.

Currently, the memtier-benchmark is hang, because the connections
to these shards are not disabling their read/write events

shard_connection.cpp

@@ -472,14 +472,6 @@ void shard_connection::process_response(void)
 
     fill_pipeline();
 
-    // update events
-    if (m_bev != NULL) {
-        // no pending response (nothing to read) and output buffer empty (nothing to write)
-        if ((m_pending_resp == 0) && (evbuffer_get_length(bufferevent_get_output(m_bev)) == 0)) {
-            bufferevent_disable(m_bev, EV_WRITE|EV_READ);
-        }
-    }
-
     if (m_conns_manager->finished()) {
         m_conns_manager->set_end_time();
     }
@@ -508,6 +500,14 @@ void shard_connection::fill_pipeline(void)
         // client manage requests logic
         m_conns_manager->create_request(now, m_id);
     }
+
+    // update events
+    if (m_bev != NULL) {
+        // no pending response (nothing to read) and output buffer empty (nothing to write)
+        if ((m_pending_resp == 0) && (evbuffer_get_length(bufferevent_get_output(m_bev)) == 0)) {
+            bufferevent_disable(m_bev, EV_WRITE|EV_READ);
+        }
+    }
 }
 
 void shard_connection::handle_event(short events)